The present invention relates generally to cleaning compositions, and more particularly, to organic compositions of low toxicity which are useful in cleaning oil and carbon residue-encrusted metallic surfaces, such as those found on auto parts and the like.
In its most specific embodiments, the invention concerns particularized formulations having ingredients adapted to combine synergistically to provide improved ability to dissolve or emulsify the combination of deposits commonly found on auto, aircraft or other mechanical parts or components. These soils include raw or baked-on oils, greases, and the like; dirt of all kinds entrained therein, varnishes and like residues from oil, fuel, solvents and other sources, and refractory materials such as carbon or carbon-containing deposits which are strongly adhered to the parts in a form of tenacious, solid crusts. The carbon residues in question are usually those resulting from exposure to fuels and lubricants at extremely high temperatures, usually over a long period of time.
In order to be useful as cleaning composition for auto, aircraft and like parts, the compositions used must not be unduly corrosive to iron and ferrous alloys such as steel; aluminum and aluminum alloys of various kinds; die cast materials such as zinc or zinc-related materials; or other miscellaneous nonferrous materials, such as brass and bronze parts containing copper and tin, for example.
Prior art compositions used for cleaning auto parts are usually embodied in immersion cleaner solutions. Parts are placed in these solutions and allowed to soak, with or without agitation, for a period of time ranging from a number of minutes up to several hours, and sometimes overnight, for example. As a result of such soaking, various oily residues or the like are emulsified or pass into solution. After this, further residue removal may be undertaken by mechanical means, such as by brushing or scrubbing.
This immersion cleaner approach with room temperature soaking has been characterized in the prior art by the use of a mixture of aliphatic or aromatic solvents particularly, including chlorinated solvents and one or more phenol or cresol derivatives, in combination with one or more soaps or detergents having an oleophilic portion chemically resembling the oil and grease to which the parts have been exposed. Typical of such compositions are those previously marketed by the assignee of the present invention; these include, for example, major parts of methylene chloride, orthodichlorobenzene, cresylic acid and a petroleum sulfonate, with minor amounts of inhibitors and in some cases a complex amine. In such compositions, the oleophilic portion of the sulfonate dissolves in the oily residues and, upon washing with water, the residues are emulsified in the water and carried away. The combination of methylene chloride and the chlorinated aromatic solvents dissolve varnishes and other residues on the parts, while the phenol and phenol-related compositions are effective to remove carbon. This prior art approach has been quite successful for cleaning purposes, but has serious environmental drawbacks. As the risks of having such compositions become more fully appreciated, the risks are viewed with increasing apprehension by an environment-and health-concerned public.
From the foregoing, it will be noted that this kind of prior art immersion cleaner has been primarily concerned with using a mix of materials having plural, functional groups each suited to its intended purpose, and using different combinations to remove a variety of residue at room temperature. The immersion cleaner approach has also been taken in regard to cleaning nonferrous materials, such as carburetor parts. A similar approach has been taken with the composition wherein p-cresol and methylene chloride have formed the primary ingredients, with a tall oil fatty acid, and perhaps 2%-5% KOH being used, with or without a supplemental ionic or non-ionic detergent. These materials are suitable for cleaning materials such as the bowls, bases, and covers of most carburetors, but are not recommended for long exposure to brass parts in view of the caustic nature of the composition. Also, strong caustic compositions of any kind are not recommended for cleaning aluminum parts for obvious reasons.
Various military specification ("Mil-Spec") cleaners have also been specified which use a mixture of cresol, phenol, oleic acid, KOH, methylene chloride and a minor amount of a chelating agent such as EDTA (ethylenediamine tetraacetic acid). In the military specification compound known as Mil-C-19853C, 55% methylene chloride is used with 34% cresol, about 2% KOH, and 6%-7% oleic acid is present. Hence, the major part of the caustic is taken up in forming effective soaps. This product may be considered safe under some circumstances when used with aluminum and various aluminum alloys, clad aluminum products, steel, and magnesium with pickled surfaces. Reference is made to U.S. Government Printing Office Publication 1982-505-022/2671 for a further explication of this formula and its use.
Another military specification cleaning composition for carbon is identified as Mil-C-25107B (USAF). The chemical composition referred to in this reference is 53% by weight o-dichlorobenzene; 23% cresylic acid; a 10%-12% potassium oleate, with the composition containing not more than 10% of a mixture of water inhibitors and other materials.
The foregoing compositions typify materials used by formulators seeking to obtain a broad band cleaner which is effective on oily, greasy, and carbon-encrusted parts, but which will not damage the underlying parts themselves.
Certain other particular cleaning and solvent applications have called for the uses of different solvents for basically different but somewhat superficially related applications. These include the use of so-called dibasic ester solvents in connection with aromatic solvents and monoethanolamine and heterocyclic amines for paint strippers, for example. Some of these include using an aromatic solvent, a dibasic ester, N-methyl-2-pyrrolidone and with or without a minor part, such as 2% or less of monoethanolamine. These formulations are non-aqueous, water insoluble formulations used in stripping and solvent activity. However, these compositions are not water soluble or water dilutable.
Inasmuch as automobiles are making increasing uses of aluminum and other nonferrous materials, and bearing in mind that individual mechanics are not necessarily aware of the identities of various material which may be placed into contact with a cleaning solution, there is significant risk of damage to parts if an improper solvent or cleaning solution is selected. In this connection, merely by way of example, whereas cylinder heads on American automobiles in the past have been made almost exclusively from iron or steel alloys, aluminum cylinder heads using bronze valve guides are now in extremely common use; more and more accessory parts include aluminum or nonferrous alloy parts, while still other parts are made from specialty materials of various kinds. Hence, it is of paramount importance that cleaning solutions which are highly corrosive to these materials be avoided.
Another common prior art practice in cleaning carbon-encrusted and otherwise dirty materials has been the so-called hot tank method. This normally involves soaking parts for an extended period in a tank having a relatively high concentration of caustics such as KOH or NAOH, together with appropriate soaps and perhaps minor proportions of solvent. Articles such as engine blocks, for example, are often soaked for many hours in a tank filled with this kind of solution at temperatures ranging from 80.degree. to 200.degree. F. While this is highly effective for degreasing or related purposes, needless to say, aluminum and other nonferrous parts are totally intolerant of such treatment, and would be seriously damaged by even a very short exposure to such methods.
Reference has been made above to the recently discovered health hazards using a number of the materials identified above. In this connection, individual investigators, as well as government agencies, such as the Environmental Protection Agency (EPA) and others have now discovered that not only are many solvent compounds such as methylene chloride, relatively toxic to humans in high concentrations, but also that even low exposure may be harmful to users or to the environment over a period of time.
Moreover, other recent studies have shown that compounds previously believed to be relatively benign may have toxicities which have not been fully appreciated, or which may have been mistakenly believed to be of a lower level than is actually the case. In this connection, workers using these types of materials may often be doing so under conditions of restricted ventilation, or may be exposed to such products over a period of time which is longer than is now considered safe.
It has also been generally assumed that where a particular composition is of a certain toxicity, its analogs and homologs would have proportional if not equal toxicity. Consequently, the use of some compounds may not have been attempted because it was assumed that such compounds are also relatively toxic. As a consequence, some attempts have been made simply to use lower concentrations of effective cleaning materials, to better protect workers from contact with them, or to attempt to clean parts by mechanical methods.
None of these solutions is entirely satisfactory, and consequently, there has been a strong need for cleaning compositions which are effective to remove deposits of oily and greasy substances, varnishes, and encrusted materials such as baked-on carbon deposits, from the surfaces of a variety of substrates, including iron, steel, and various ferrous alloys; aluminum, brass, and other metals and alloys including magnesium, ferrous parts coated with chromium or cadmium, for example, and the like.
According to the present invention, it has been discovered that effective cleaning compositions may be made from a mixture of various ingredients which may include, in varying concentrations, certain glycol ethers (or esters derived from those ethers), aliphatic fatty acids such as oleic acid, amines, and alcohol amines, a minor portion of a very mild caustic such as ammonium hydroxide and water. Such compositions may include aromatic solvents such as cumene, or aliphatic solvents, with the aliphatic acids or the glycol ethers and their derivatives serving as couplers for the oil and water solvent and emulsion systems thereby created. The resulting composition is as effective or more effective than prior art compositions for cleaning oil and grease from automotive parts, and yet it provides greatly reduced short- and long-term exposure hazards.
It is accordingly an object of the present invention to provide a series of formulations for cleaning auto parts, which formulations present greatly reduced toxicity and health hazards.
Another object of the invention is to provide cleaning compositions for use in removing various kinds of soil from auto parts, and which are tolerant of a wide variety of materials from which such parts are made.
A further object of the invention is to provide a parts cleaning composition which contains materials which are not corrosive to the skin or hazardous to human health and which may be used as an immersion cleaner at room temperature.
A still further object of the invention is to provide cleaning compositions which use as a principal component one or more ethers or ether ester derivative compositions in combination with selected cyclic amines and alcoholic amines.
Yet another object of the invention is to provide a parts cleaning compound which is relatively safe for human use and which may include, in varying proportions and concentrations, propylene glycol methyl ether, propylene glycol monomethyl ether acetate, N-methyl pyrrolidone, ethanolamine, aliphatic acids and minor parts of ammonium hydroxide and water, with such composition being useful in auto parts cleaning.
Another object of the invention is to provide a composition of the type just described above which may further include a high boiling relatively nontoxic aromatic material.
A still further object of the invention is to provide a composition having a glycol ether or glycol ether acetate component in an amount of about 5% to about 80% by volume percent, a pyrrolidone or a cyclic amine in an amount of about 5% to about 35% by volume percent, and other materials in minor amounts.
The manner in which the foregoing and other advantages of the object are achieved in practice will become more clearly apparent when reference is made to the following examples of practicing the invention and the discussion set forth elsewhere herein.